Boiling Heat Exchanger

[Analgesic]

Question for the chemists-I have read on this forum that the heat exchanger should be taken to a radiator shop to be boiled out periodically.  I removed mine this week and it was dramatically caked with scale on the inside.  I called my local radiator shop and he says he stopped doing any boiling years ago once car radiators became more plastic.  So, being from New England, I do have a big lobster pot that would easily accommodate the exchanger.  Any suggestions how I might boil it myself?  With vinegar or some other safe chemical?  Thanks in advance for any guidance. 
Brian McPhillips

[mark_53]

Congratulations on having a boat that is in such good shape that you have nothing else to fix!  If the HX is still working I would leave it alone.  I just replace mine when I noticed my antifreeze was replaced with salt water  .  Make sure you check the zinc at least every 2 months if you are in salt water.

[KWKloeber]

Congratulations on having a boat that is in such good shape that you have nothing else to fix!  If the HX is still working I would leave it alone.  I just replace mine when I noticed my antifreeze was replaced with salt water  .  Make sure you check the zinc at least every 2 months if you are in salt water.

HUH? What?? 
Don't bother with maintenance? 
Why even bother looking at a zinc?  If it's working, leave it alone, right?
Hey, if your seawater pump impeller is missing a few, Don't Worry--Be Happy.  Don't change it so long as it's pumping.

sheesh.

Ken

[KWKloeber]

Brian,

Vinegar might work, but would take forever. As might C-L-R or Lime-Away.

The most effective is using boiler descaler, which is muriatic acid (available at many hardware and the big box stores) -- and is also used for cleaning concrete.  

HOWEVER, any concentrated acid is dangerous unless used properly WITH appropriate personal protective equipment.  Though it certainly can be used by the non-professional, it sounds like (since you're not familiar with it) you might not want to attempt it.   I regularly use muriatic acid to descale groundwater treatment system components, so know all the "safe" ins and outs (but for obvious reason of encouraging the average Joe to try it,  I'm not going to publish them here.)

RydLyme (rid-lime) is a much safer alternative that works near the "scale" that muriatic acid does (pun intended).  It's typically found only in industrial supply distributors, but give a call or drop a webmail and they might have a stocking dealer near you.
http://www.apexengineeringproducts.com/products/rydlymedescaler/

Having a lobster pot is ok but I use a plastic storage container (e.g., Sterlite, Rubbermaid)  You don't want to dump the Hx in a tub of RydLyme and let it sit.  The key is constant movement of the RydLyme across the scale.  If you dump the Hx it in a tub, a boundary layer soon establishes that equilibrates near the concentration of the scale, and so very little transfer occurs between the Hx scale and the RydLyme.  We're talking Henry's Law here, if you've ever met up with him.

Think of it this way... hot engine coolant running thru a HX that's sitting in a tub of ice-water will heat up the tub, and your engine will overheat because no more heat is transferred out of the coolant.  But circulate even luke warm water and the Hx and engine are both happy.

So you want to keep the RydLyme moving against the scale -- ie, circulating thru the Hx.  
A small pump works well.  The smaller the container the better (tall but w/ a small footprint).  Fill it enough so that there's a reservoir so the pump can draw up the RydLyme (can tip the container so you have a pool at one end); pump the RydLyme thru the Hx; letting it discharge into to the tub; pick it up w/ the pump again -- continuing that cycle until the scale is gone or the descaler is spent (no longer "acts on" the scale.)  Depending of course on how much scale you have and how much RydLyme you use, you might need to use "fresh" RydLyme to remove the last 10%.  You're better off using less, and then freshening it midway -- than using the entire gallon at once.

A utility pump like this works well (I might add a cheap inline ball valve to throttle the flow.)
http://www.harborfreight.com/12-volt-marine-utility-water-pump-94639.html
These type utility pumps are available in 120v, but not at HF
http://www.tractorsupply.com/en/store/countylinereg%3B-transfer-utility-pump-1-12-hp

Or use a drill pump
http://www.tractorsupply.com/en/store/water-source-drill-pump


BUT, the 12v pump has at least 10 other uses if kept aboard.
I set mine up w/ an inline rocker-switch, a long 12v plug-end cord, and in addition to the garden hose threads -- have hose barbs on the inlet/outlet (for an oil change pump, tranny fluid change pump, emergency diesel fuel pump, diesel tank emptying pump, wash down pump, emergency seawater cooling pump, emergency (tho low flow) bilge pump, engine block emptying pump, thru-hull weed clearing pump, water system pink stuff pump.)

A fountain pump would also work, but with that I might try sitting the Hx upright w/ the ends open, pump the RydLyme to the top end, and let it gravity flow thru the tubes.

Ken K

[Stu Jackson]

We recently had a discussion about HXs, and this one covers a lot of ground, mostly though on replacement, just in case you may need to.

http://c34.org/bbs/index.php/topic,6920.0.html

It touches on salt precipitating into the inlet port (I found this link by searching for "inlet port" - it might be in the "101 Topics," too).

I continue to recommend removing and inspecting the HX every two or three years.  Or until the mounts breaks.  Whichever comes sooner!  

Ken's right in terms of inspecting the entire raw water cooling system, though.  You may already have done this and narrowed it down to the HX by now.

Good luck.  It's always something!    Nice part is its always accessible on our boats.  

[Noah]

Good discussion. I stayed out of the intial fray, although it sounded very starnge to me that you would change the zinc every two months and then "suddenly discover that saltwater had replaced the cooling". Maybe satire?

In any case I am about to remove mine and take it to the the shop in San Diego for reconditioning for a few reasons:
1. I have only owned the boat for barely 1 yr. and don't know any maintenance history
2. I replaced the zinc (once) and had to knock the other semi-depleted zinc into the heat exchanger to facilitate installing a replacement zinc
3. I am not a mechanic, but upon the advice of one, and listening/reading the web boards, have decided after 20+ years (in my case an unknown time interval since last done) it's prudent to refurbish. Small price to pay to avoid engine overheating issues. My mechanic said he has a shop he "takes them to all the time". Apparently the plastic age isn't a problem in this Navy town.  His only worry was I would be "down" for a week so he advised me to "wait until summer was over" . LOL!  It is always Summer in San Diego.

[Mike and Joanne Stimmler]

Brian,
I think you should check out a few other radiator shops, There's bound to be one that can do the job and then you'll know that it's been done professionally and you won't have to mess with any nasty chemicals,
You can also give it a nice coat of paint after it's all nice and clean. My two cents.

Mike

[KWKloeber]

very starnge to me that you would change the zinc every two months and then "suddenly discover that saltwater had replaced the cooling". Maybe satire?

The zinc doesn't necessarily prevent eating a pinhole thru one of the Hx tubes, in which case the engine coolant (higher pressure) will push into the sea water side of the Hx (lower pressure) and you will loose coolant regularly.  Mine did at ~15 years on a 100% freshwater boat.  

Opening the pressure cap helps reduce coolant loss 9and overheating) on a short-term basis until the HX is replaced.  I have never, ever, in 30 years of dealing with Hxs and seawater pumps, heard of a seawater pump being able to overcome the 13-15 psi present in the closed coolant side (engine block,) and replacing the engine coolant.  I suppose if the situation was totally ignored until it became critical (similar to never performing maintenance on a HX) something strange could happen, given certain circumstances.But overheating would be a clue before that happens.

Noah, if you don't have a Copper-Nickel Hx, I would consider investing in one rather than spending boat bucks on "reconditioning" (whatever the shop includes in that I have no idea except descaling and new gaskets.)

Ken K

[Noah]

Thx for info Ken. I "believe" mine is copper/nickel from the looks and "feel" of it when I changed zinc. It is a 3 in. Guess until it is removed I won't know for sure or if it just needs a cleanout/descale and gaskets or a replace.

[Stu Jackson]

very strange to me that you would change the zinc every two months and then "suddenly discover that saltwater had replaced the cooling". Maybe satire?

The zinc doesn't necessarily prevent eating a pinhole thru one of the Hx tubes, in which case the engine coolant (higher pressure) will push into the sea water side of the Hx (lower pressure) and you will loose coolant regularly.  Mine did at ~15 years on a 100% freshwater boat.

Zinc replacement periods:  Good point to check regularly.  As previously reported, my zinc changes have been anywhere from as often as 2 to 2 1/2 months to six.  Doesn't vary 'cuz boats near me may have electrical issues since my neighbors seldom change and/or change their "being plugged in all the time" status.  It's either "What's in YOUR water?"  or the quality of the zincs I buy (usually from the same source).

I think it's VooDoo, but I check regularly and keep track.  Now a check every three months - quarterly - works, and has for the past ten years.  YMMV.  

And, yes, Ken's right, the tubes and shell are independent pieces and could, and may, react differently.

My take is that if you have ANY questions about the "solidity" or integrity of your HX, just buy a new one.  Given the cost of the boil out - certainly dependent upon your source for that service - compared to a new one (as detailed in the earlier link) - it's your call.

Your boat, your choice.

What's a new engine worth to ya?  

[Les Luzar]

Brian,
I just finished servicing my HX because my temperature gauge was beginning to run hotter and I was also experiencing white steam out the exhaust. I was beginning to run at 180 degrees at low RPM and 190 degrees at cruising speed. So I removed the HX and found that the raw water input was 80% clogged and the HX was in just as bad a condition. So I reviewed the past posts and decided to soak the HX in CLR. After which I cleaned it with fresh water, primed it with engine primer, and painted it with bronze engine paint. Then I installed new end caps and rubber washers. It turned out fine. Also, there were a few tubes that had a blockage, that I cleared out with a 15 inch bicycle brake line on my electric drill. I re-installed it burped the engine, and it was good to go. My engine is now running at normal temperatures. You may want to try the CLR first. It was simple and worked really well.  See the attached pictures....

[Ralph Masters]

Good job Les.  When I did mine last year I got a product similar to CLR at Home Depot but it was about 5 times stronger, don't recall the name.  I stood the HX up in a 5 gallon bucket and poured the cleaner in and let it work.  About a 1/4 of the HX was sticking up so every 5 minutes or so I'd pull it out and turn it over.  Wear gloves and eye protection.  It came out looking like the one in Les' photo.
I put new end caps, new end cap gaskets and the rawhide washers on the bolts and put it all back together with a new zinc.  It sits in the bottom of the dock box along with a rebuilt raw water pump.  I figure when I have to replace one, I'll replace both.
FWIW-I pull and change the HX zinc every 3 months, for you navy guys it's a Q-1R.  I put it in my google calendar for every 3 months and the phone emails when it's time to change. 
Same with oil changes, every 6 months, S-1R, no matter how many hours I have.  I figure the environment dictates that.

Ralph

[Analgesic]

Well, calling around, I found another radiator shop about 20 miles away that will do the boiling job the old fashioned way.  Mine only looked half as bad as the pictures posted so I guess there is still plenty of life left in it.

[KWKloeber]

Well, calling around, I found another radiator shop about 20 miles away that will do the boiling job the old fashioned way.  Mine only looked half as bad as the pictures posted so I guess there is still plenty of life left in it.

Brian,

Just for peace of mind, make sure they pressure test it both beforehand and afterward.  Being (presumably) 26 years old, one of those pinholes may he ready to let go.  As I said. mine went south at ~15 years, but it was not Cu-Ni construction.   

Tube integrity won't be evident from the outside condition or the amt of scale visible inside.  Pressure test before -- so that if there's a slight leak they don't charge you for "boiling" it out, and afterward -- so that if scale was blocking a pinhole you don't reinstall it.

What's the going rate these days for "reconditioning," and what does it cover?  Let us know how you make out!

kk

[Mike and Joanne Stimmler]

You might ask if they can repair it if there is a leak. It might be a simple job for a radiator shop. I'm pretty sure they can repair leaks on radiators for cars. It never hurts to ask.

Mike